Help creating a universal rig?

I am trying to create universal animations that will work on both R6 and R15, so I will not have to check the players humanoid rig type at runtime

To do this I created a custom R21 rig by merging all the parts in an R6 and R15 rig, but since Head has the same name in both rigs, but is connected to different parts, how should I handle that? The animation editor refuses rigs with >1 parts of the same name, or a part connected by >1 Motor6D joints

If I simply rename one or both of the heads, then when a player is animated, the head will not be recognized

What should I do?

There is no way to get the Animation Editor to handle an actual universal rig

I need to get the KeyframeSequences for the R6 and R15 animations and properly merge them, then upload to Roblox

Uploading a KeyframeSequence will upload as an Animation instead of a Model

Then I have a universal animation in a single asset